This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-283766, filed Oct. 5, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a solution processing apparatus and method for supplying a developing solution to a front face of, for example, a substrate coated with a resist and subjected to exposure processing, thereby to perform developing processing.
A mask for forming a circuit pattern on a front face of a semiconductor wafer (hereinafter, referred to as a wafer) or an LCD substrate of a liquid crystal display is formed as follows. Initially, a photoresist solution (hereinafter, referred to as a resist) is coated on a front face of a wafer and irradiated by light or the like. If the resist is a negative type by way of example, a portion thereof applied with light is cured, and a portion not cured, an easy-to-dissolve portion, is dissolved with a developing solution, whereby an object mask is formed. A developing processing apparatus comprises a spin chuck for vacuum-holding and rotating a wafer and a developing solution supply nozzle for supplying a developing solution to the wafer on the spin chuck.
Conventionally, a supply nozzle in which many discharge ports are arranged over an area corresponding to a wafer W in a diameter direction is used as the developing solution supply nozzle used in a developing step as described above.
The discharge of the developing solution by the supply nozzle will be explained. The supply nozzle is positioned so that the discharge ports are, for example, 1 mm above the front face of the wafer W at the middle portion of the wafer W, and the wafer W is rotated 180 degrees while the developing solution is supplied from the discharge ports to the middle portion in the diameter direction of the front face of the wafer W. Thereby, the developing solution is spread over the entire wafer W while being discharged from the middle portion in the diameter direction of the wafer W, in a result that solution heaping is completed. Simultaneously, a developing solution film with a predetermined thickness is formed on the entire front face of the wafer W.
Conventionally, in the step of heaping the developing solution over all of a top face of the wafer, it is required for obtaining uniformity of line width to close to the same as much as possible. To this end, the developing solution needs to be rapidly applied to the wafer, and thus a supply pressure of the developing solution is kept high.
However, in the conventional developing processing method, the developing solution supply nozzle is formed so that the discharge ports thereof are small in diameter and the supply pressure thereof is set high for the sake of uniform discharge, resulting in high discharge flow velocity. Therefore, an impact on a dissolved portion of the front face of the wafer is high at the time of initial discharge to the front face of the wafer, whereby the uniformity in line width is susceptible to decreasing.
Further, there exists a portion where the first discharged developing solution and the last discharged developing solution are overlapped within an area close to the middle of the wafer under the supply nozzle, whereby old and new developing solutions are mixed and thus developing proceeds in the portion more than in other portions, thereby also bringing about a danger that uniformity in line width of the area close to the middle deteriorates.
Additionally, since the developing solution is discharged while the wafer is rotated, solution face waviness occurs at the time of heaping of the developing solution caused by inertial force of the developing solution and there occur an area where the developing solutions are vigorously mixed and an area without such vigorous mixture, thereby bringing about a disadvantage that the uniformity of the developing becomes worse.
There is a scan-type coating means using the same developing solution supply nozzle as the aforementioned, in which the supply nozzle is placed at the outside of the rim of the wafer W and moved therefrom to the outside of the rim of the wafer on the other side while performing discharge.
For example, in such a scan-type coating means, when the supply nozzle 12 passes through an area above the wafer W and leaves a position above the end portion of the wafer W, the developing solution near the discharge ports 11 of the supply nozzle 12 is caused to be in a state as shown in FIG. 10A, wherein the developing solution applied on the front face of the wafer W and the developing solution supplied from the discharge ports 11 are stretched (see portion P) while they are contiguous with each other by respective surface tensions.
However, when the discharge ports 11 leaves the developing solution due to the movement of the supply nozzle 12, a pull back phenomenon occurs in reaction thereto in which the developing solution at the portion P stretched by surface tension returns to the edge portion of the front face of the wafer W. This causes a problem that the developing solution is supplied more on the front face at the rim portion of the wafer W than on the front face of the other parts of the wafer W as shown in FIG. 10B, which brings about a disadvantage that line width becomes nonuniform.
It is an object of the present invention to provide a solution processing apparatus and a method thereof capable of performing uniform solution processing on a front face of a substrate.
According to a first aspect of the present invention, there is provided a solution processing apparatus comprising: a substrate holding portion which horizontally holds a substrate; a supply nozzle which moves from one end side to the other end side of the substrate held by the substrate holding portion to perform supply of a processing solution to a front face of the substrate; and a solution separation ring provided to surround a periphery of the substrate with a slight clearance therebetween to separate the processing solution existing between the other end of the substrate and the supply nozzle by surface tension from the substrate and allow the developing solution to adhere to the solution separation ring when the supply nozzle leaves the other end side of the substrate outward, the solution separating ring being made of a material with adhesion to the processing solution stronger than that of the substrate.
With the above configuration, occurrence of a pull back phenomenon can be prevented when the supply nozzle leaves the other end side outward, so that uniform solution processing can be performed over the entire front face of the substrate.
According to the second aspect of the present invention, there is provided a solution processing method comprising the steps of; holding a substrate on a substrate holding portion; supplying a processing solution to a front face of the substrate while moving a supply nozzle from one end side to the other end side of the substrate held by the substrate holding portion; allowing the processing solution to exist among a solution separation ring provided to surround the substrate with a slight clearance therebetween, the other end of the substrate, and the supply nozzle by surface tension when the supply nozzle leaves the other end side of the substrate outward; and thereafter allowing the processing solution to leave the other end of the substrate and adhere to the solution separation ring when the supply nozzle moves further outward.
With the above configuration, occurrence of a pull back phenomenon can be prevented when the supply nozzle leaves the other end side outward, so that uniform solution processing can be performed over the entire front face of the substrate.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.